Proponents of UK Biobank, a genetic repository, believe that it heralds an era of "designer medicine" where treatments are customised and people at risk from allergies, drug side effects and serious illnesses can be identified.

But unease about the project has been voiced by Sir David Weatherall, professor at Oxford University's Weatherall Institute of Molecular Medicine and a pioneering researcher in molecular genetics.

Sir David is the lead author of a World Health Organisation report, published a few days ago, that warns that large-scale genetic databases present hazards and ethical issues which have not been previously encountered.

The UK Biobank project, hailed as the world's largest study of the role of nature and nurture in health and disease, is backed by the Wellcome Trust, the Medical Research Council and the Department of Health.